Twin to Twin Transfusion Syndrome (TTTS) is a serious complication of an identical twin pregnancy in which there is only one placenta. TTTS occurs in 10-15% of identical twin pregnancies. When TTTS occurs, there is an unequal sharing of blood between two fetuses due to blood vessels that communicate between the two fetuses in the single placenta. In the most serious cases, one fetus (called the Recipient twin) is larger and surrounded by an excessive amount of amniotic fluid, while the other fetus (known as the Donor twin) is smaller and appears to be stuck against the uterine wall due to the reduced amount of amniotic fluid.
The pregnancy may be lost from heart overload in the larger twin, lack of enough blood getting to the smaller twin, or preterm (early) labour because of the excess fluid causing the uterus to be ‘overstretched’
What are the available treatment?
If not treated, severe Twin to Twin Transfusion Syndrome has a mortality rate close to 100%. Current treatment methods include:
- Serial Amnioreduction (regular removal of the amniotic fluid from the womb with a needle)
- Septostomy (making a hole in the separating membrane with a needle)
- Umbilical Cord Occlusion (Stopping the blood flow in one of the baby’s cord)
- Laser photocoagulation of the communicating vessels
Why laser photocoagulation of the communicating vessels?
In this form of treatment, the laser is used to seal the vessels to stop the blood flow between the fetuses. This is the only definitive form of treatment as it targets the underlying pathology or problem which is communicating vessels between the two babies on the placenta. The reported outcome in overseas is 85% survival rate for at least one baby and 50 to 75% for both, with an incidence of neurological complications of 2 to 5%. This is much better than the other forms of treatment mentioned above.
What are the risks associated with this procedure?
There are potential complications associated with this procedure:
- There is the possibility of bleeding in the mother and/or fetuses, which could prevent the completion of the procedure.
- Rarely, bleeding may be of such magnitude that we may need to make an abdominal incision (laparotomy) and place a suture on the uterus.
- Preterm labor, amniotic fluid leakage or premature rupture of membranes could occur. If any of these complications occur, we may need to keep the mother in the hospital. Infection of the amniotic cavity may also occur and lead to these complications. If infection is diagnosed, delivery is required to prevent further complications.
- Placental abruption or separation has been rarely reported
There is a low incidence of these complications as precautions are taken to minimize these risks. Patients are placed on antibiotics to prevent infection. Very small instrumentation is used to help prevent bleeding and preterm labour. All patients are evaluated thoroughly prior to this procedure.
How is this procedure done?
You will be admitted a day before the procedure in hospital. You will be asked to fast overnight. The following morning, you will have another ultrasound scan to evaluate the condition of your babies. The procedure will usually be done under sedation and local anesthesia. In a minority of cases it will be done under general anesthesia. The procedure usually lasts around 2 to 3 hours (from the time the patient is wheeled into the OT till the patient leaves). A small incision (1cm) is made in the mother’s belly to insert a fetoscope and laser fiber, under combined ultrasound and fetoscope guidance. The fetoscope is a long, narrow telescope with a light and camera on the end. The blood vessels are identified and sealed through the fetoscope. The purpose of surgery is to separate the circulation between the babies by using the laser to seal the vessels connecting the two. In essence, these babies are now like fraternal twins. They are no longer sharing blood and each has its own portion of the placenta.
What happens to me after the procedure?
After the procedure, you will be rested in the High Risk Antenatal Ward for 1 day. A repeat ultrasound is done to assess the wellbeing of the fetuses. If you have preterm contractions, you will be treated with medication that will help to stop the contractions. You will usually be discharged the day after the procedure if there are no complications. You will be followed up at the centre which referred you on a regular basis and subsequently delivered in that centre at a gestation which will be advised by the MFM consultant from hospital in consultation with the managing obstetrician or MFM specialist. The recommended gestation of delivery for uncomplicated cases of post laser treated TTTS is 36 to 38 weeks. Most of the time you will need delivery via Cesarean section.